Novak Djokovic

Novak Djokovic of Serbia lifts the trophy after defeating Rafael Nadal of Spain in their men's final singles tennis match at the ATP World Tour Finals at the O2 Arena in London November 11, 2013.

Novak Djokovic of Serbia lifts the trophy after defeating Rafael Nadal of Spain in their men's final singles tennis match at the ATP World Tour Finals at the O2 Arena in London November 11, 2013. (DYLAN MARTINEZ / REUTERS)

Novak Djokovic of Serbia lifts the trophy after defeating Rafael Nadal of Spain in their men's final singles tennis match at the ATP World Tour Finals at the O2 Arena in London November 11, 2013.